How to Grow Giant Collard Green Species

Soil and Light

• Tree collards grow best in full sun, although it is good to have some dappled or late afternoon shade on the hottest summer days. Newly planted cuttings should have a shade cloth or lawn furniture placed nearby in the afternoon for shade. It is helpful to have a soil pH between 6.0 and 6.8; a soil test kit can tell you what your soil pH is. About three weeks before planting the collards, dig or till 4 to 6 inches of compost or aged manure into the top 6 to 12 inches of soil to enrich it. Space multiple plants at least 3 feet apart.

Planting

• Collard trees are planted from 6-inch cuttings in the fall in their hardiness zones so they are not exposed to summer heat until they are established. Outside these zones the cuttings can be planted as annuals in the spring after frost danger has passed. Purchased cuttings will be ready to plant -- you just need to cut up to 1 inch from the bottom of the cutting to remove the dried end. If you take your own cutting, cut a 6-inch section of stem tip from a non-woody part of a mature tree. Remove the leaves from the cutting before planting. Plant cuttings with 2 to 3 inches of cutting above the soil surface; at least one-half the cutting needs to be below the soil surface. The nodes, or small notches along the stem, should have the dip pointing downward -- otherwise you will be planting your cuttings upside down.

Water and Fertilizer

• Newly planted cuttings need moist soil and should be watered at least 2 to 3 inches per week. While established plants are more drought tolerant, the greens will taste better if you continue to provide at least an inch of water per week. A 2-inch layer of organic mulch will help keep soil moist. Sprinkle a 33-0-0 fertilizer per plant over the root zone and water the fertilizer into the soil twice per year -- in the spring before new growth begins and in early fall for an abundant winter harvest. For tree collards grown as annuals, fertilize about five weeks after planting and again about one month before the first expected frost. Follow the manufacturer's label instructions to determine the appropriate rate.

Pruning

• You may prune your tree collard yearly to keep the plant smaller and keep leaves larger, or you can let the tree collard grow naturally. If you allow the collard to grow to its full height, you will likely need to stake the plant when it gets over 3 feet tall. You can cut leggy plants pack to between 2 to 3 feet tall each year in mid-summer before the hottest summer temperatures hit. Cut about 1 inch above a node to promote new growth. You can also remove any weak or woody growth at this time.

Pests and Diseases

• Pests that bother tree collards include cabbage worms and aphids. Check the undersides of leaves for aphids, which look like moving specks. Holes in the leaves can indicate the presence of worms. A weekly pressured spray of water to wash the leaves will help eliminate aphid infestations. Control cabbage worms with an insecticide containing Bacillus thuringiensis, or BT. Apply the insecticide on a cloudy day. Mix 1 to 2 teaspoons of insecticide in 1 gallon of water. Spray up to a 50-foot row of collards with each gallon of mixture, thoroughly covering the leaves. Powdery mildew can also be a problem. Avoid getting the leaves wet or crowding plants to prevent mildew. You can also spray leaves with a premixed fungicidal spray.